Career Summary

Biography

I have made significant contributions to the fields of polymeric surface coatings and atomic force microscope (AFM) colloid probe force measurements, as evidenced by my solid record of publishing in international journals of high impact factor. I pioneered the use of AFM to image in-situ the development of films of polymer micelles adsorbed from aqueous solution onto solid substrates. I was the lead author of the first report to observe in-situ morphological changes in an adsorbed film of copolymer micelles in response to a change in aqueous solution pH. A subsequent article, again as lead author, was the first-ever report of reversible stimulus-responsive behaviour of micellar thin-films where the behaviour was in reaction to a simple aqueous solution based trigger. The novelty of this work in the context of coatings for controlled surface interactions cannot be underestimated.

My research methodolgy for understanding the properties of polymer adsorption is the combined application of a number of specialised scientific methods, such as atomic force microscopy, quartz crystal microbalance, electrophoretic mobility, contact angle and surface tension, and dynamic and static light scattering. This holistic approach has extracted significant new knowledge on the fundamental processes of polymer adsorption, and has enabled rigourous investigation of the link between microscopic changes in the morphology of polymer films and macroscopic properties such as wettability. I have recently started investigating ionic liquids. Ionic liquids are composed entirely of ions, and yet are liquid at room temperature, offering intriguing properties such as a wide solubility window and a high degree of molecular ordering when confined at a solid interface. Along with Dr Rob Atkin, for the Chemistry department at the University of Newcastle, we are investigating the properties of colloidal dispersions is ionic liquids, and probing important frictional and hydrodynamic forces. Previous work at the University of Melbourne focused on the use of atomic force microscopy to measure the interactions between deformable interfaces. Here I overcame the extreme technical difficulties of using an oil drop as a colloid probe, demonstrating my skills as an experimentalist.

Research ExpertiseMy research uses engineered surfaces and interfaces to control material properties. By combining the disciplines of chemical engineering and physical chemistry my research aims to solve real-world problems through the application of fundamental science. I have an extensive track record in the production and characterisation of stimulus-responsive polymer thin-film coatings. These coatings change their structure at a molecular level in response to external stimuli such as solution pH, temperature or salt concentration. The nanoscale switches in morphology impact macroscale behaviour, such as contact angle and wettability. Recent research has investigated the production of stimulus-responsive polymer coatings via a process known as surface initiated polymerisation. This process is water-based, has low energy requirements, and offers enhanced control of the three-dimensional structure of the coating. In this way we are able to better engineer a surface or interface to meet a specific end-use application, such as a temperature dependent rheology modifier. Another are of research is examining the effect of mixed stabilisers on the stability and rheology of emulsions, in particular highly-concentrated emulsions. Here, a combination of surfactant and particles are used to stabilise the oil-water interface. We are using dynamic and equilibrium surface tension measurements to characterise structure of the interface and relating this to emulsion stability during shear. I have recently started working in an exciting emerging field; ionic liquids. Ionic liquids have quite unusual physical and chemical properties, and are seen by many as ideal designer solvents for a range of industrial applications. My research is investigating the properties of dispersions of microscale solid particles in ionic liquids; a proposed application of ionic liquids is as solvents for catalytic reactions. We have discovered some unusual behaviour, such as high stability in conjunction with rapid settling, and are using a combination of friction, hydrodynamic and rheological measurements to further understand these remarkable class of materials. My research spans a wide range of length scales, from the nano- to micro- and up to the macroscale. As such I use an array of instruments and techniques in the course of my research: - atomic force microscopy for imaging, including soft-contact imaging in fluids, and force work - quartz crystal microbalance and optical reflectometry techniques to quantify adsorption of material at solid interfaces - dynamic and static light scattering for measuring particle sizes - electrophoretic techniques to measure particle surface charge (zeta potential) - surface and interfacial tension - contact angle - rheology

Teaching ExpertiseI am course coordinator and sole lecturer for the 2nd year chemical engineering course Particle Processing. This course covers are range of topic related to particle and mineral processing, from small scale inter-particle interactions to industrial scale unit operations. I introduce students to the fundamental processes that control the interactions between two particles, such as the Deryagin-Landau and Verwey-Overbeek (DLVO) theory that quantifies the effect of surface charge and van der Waals forces. We also examine the effect of surfactant and polymer adsorption at surfaces and interfaces, and discuss the stability and application of emulsions. The course also details unit operations important to particle processing, such as crushing and grinding, pneumatic conveying, storage hopper design, and fluidised beds. I am also strongly committed to ensuring that our chemical engineering students have adequate laboratory and practical skills, coupled with the ability to prepare coherent technical reports. To this I am course coordinator of the 2nd year laboratory course. This course uses bench-scale equipment to give the student practical demonstrations of theories they have learnt in lecture courses. These experiments include a forced air cooling tower, fluidised bed, and concentric tube heat exchanger. In this course the students are also expected to prepare technical reports, from which extensive feedback is provided so that the students are able to improve their skills in this often underrated component of engineering.

Administrative ExpertiseSince starting at the University of Newcastle in late 2007 I have been a member of the Faculty of Engineering and Built Environment (FEBE) Marketing Committee. I see this role as an important component of my job as a Chemical Engineering academic, as I believe there is great scope for increasing the profile of chemical engineering in the wider community. I am particularly dedicated to educating secondary students of the role of chemical engineers in todays society. To this I organise regular visits of my academic colleagues to high schools, as well as attending larger events, such as Careers Days, where I am able to reach a broader range of potential students. I have recently become a member of the FEBE Research Committee, which meets regularly to discuss issues that impact on research-active members of the Faculty.

CollaborationsMy research uses engineered surfaces and interfaces to control material properties. By combining the disciplines of chemical engineering and physical chemistry my research aims to solve real-world problems through the application of fundamental science. I have an extensive track record in the production and characterisation of stimulus-responsive polymer thin-film coatings. These coatings change their structure at a molecular level in response to external stimuli such as solution pH, temperature or salt concentration. The nanoscale switches in morphology impact macroscale behaviour, such as contact angle and wettability. Recent research has investigated the production of stimulus-responsive polymer coatings via a process known as surface initiated polymerisation. This process is water-based, has low energy requirements, and offers enhanced control of the three-dimensional structure of the coating. In this way we are able to better engineer a surface or interface to meet a specific end-use application, such as a temperature dependent rheology modifier. Another are of research is examining the effect of mixed stabilisers on the stability and rheology of emulsions, in particular highly-concentrated emulsions. Here, a combination of surfactant and particles are used to stabilise the oil-water interface. We are using dynamic and equilibrium surface tension measurements to characterise structure of the interface and relating this to emulsion stability during shear. I have recently started working in an exciting emerging field; ionic liquids. Ionic liquids have quite unusual physical and chemical properties, and are seen by many as ideal designer solvents for a range of industrial applications. My research is investigating the properties of dispersions of microscale solid particles in ionic liquids; a proposed application of ionic liquids is as solvents for catalytic reactions. We have discovered some unusual behaviour, such as high stability in conjunction with rapid settling, and are using a combination of friction, hydrodynamic and rheological measurements to further understand these remarkable class of materials. My research spans a wide range of length scales, from the nano- to micro- and up to the macroscale. As such I use an array of instruments and techniques in the course of my research: - atomic force microscopy for imaging, including soft-contact imaging in fluids, and force work - quartz crystal microbalance and optical reflectometry techniques to quantify adsorption of material at solid interfaces - dynamic and static light scattering for measuring particle sizes - electrophoretic techniques to measure particle surface charge (zeta potential) - surface and interfacial tension - contact angle - rheology

Transport of dry solid particles to a liquid is relevant to a number of emerging applications, including &apos;liquid marbles&apos;. We report experiments where the transport of d... [more]

Transport of dry solid particles to a liquid is relevant to a number of emerging applications, including 'liquid marbles'. We report experiments where the transport of dry particles to a pendent water droplet is driven by an external electric field. Both hydrophilic and hydrophobic materials (silica, PMMA) were studied. For silica particles (hydrophilic, poorly conductive), a critical applied voltage initiated transfer, in the form of a rapid 'avalanche' of a large number of particles. The particle-loaded drop then detached, producing a metastable spherical agglomerate. Pure PMMA particles did not display this 'avalanche' behaviour, and when added to silica particles, appeared to cause aggregation and change the nature of the transfer mechanism. This paper is largely devoted to the avalanche process, in which deformation of the drop and radial compaction of the particle bed due to the electric field are thought to have played a central role. Since no direct contact is required between the bed and the drop, we hope to produce liquid marble-type aggregates with layered structures incorporating hydrophilic particles, which has not previously been possible.

The interfacial ordering of Ionic liquids leads to interesting nanotribological properties as revealed by colloid probe studies. The first of these is the clear correlation betwee... [more]

The interfacial ordering of Ionic liquids leads to interesting nanotribological properties as revealed by colloid probe studies. The first of these is the clear correlation between the number of ion pairs trapped in the tribological contact and the friction coefficient displayed. The second is the fact that the surface electrical potential can be used to control the composition of the boundary layer and thus tune the friction. Thirdly, the interfacial ordering appears to significantly affect the fluid dynamics over large distances.

Colloidal suspension behaviour is strongly influenced by the particle - particle interaction forces operative in the system. The stability of aqueous suspensions can be manipulate... [more]

Colloidal suspension behaviour is strongly influenced by the particle - particle interaction forces operative in the system. The stability of aqueous suspensions can be manipulated though the addition of electrolyte and changes in the pH. Such adjustments affect the net surface charge of the particles and/or the thickness of the diffuse electrical double layer (edl) surrounding the particles. If the charge or the double layer is sufficiently reduced, the ubiquitous attractive van der Waals interaction forces can dominate and the dispersion is destabilized. A Quartz Crystal Microbalance with dissipation monitoring (QCM-D) is used to measure the degree of destabilisation in a particle suspension. Mono-dispersed silica suspensions were prepared in several different chemical environments, with the conditions chosen from examination of the zeta potential and sedimentation data. The study shows that by varying the suspension stability, the resonating frequency of the 5MHz AT-cut quartz silica crystal, significantly deviates as the amplitude of oscillation is increased for a coagulated suspension, whilst remaining unchanged for a dispersed suspension.

Research Collaborations

The map is a representation of a researchers co-authorship with collaborators across the globe. The map displays the number of publications against a country, where there is at least one co-author based in that country. Data is sourced from the University of Newcastle research publication management system (NURO) and may not fully represent the authors complete body of work.